In most geographic areas prior art water sources are placed far from the actual utilization point. In such cases, the ability to extract water from air offers a substantial advantage, because there is no need to transport the water from a distant source to a local storage facility. Moreover, if water is continuously harvested, local water reserve requirements are greatly reduced.
Another reason for water-from-air extraction is in those regions of the world where sources of potable water are scarce or absent.
An exemplary situation is when a massive forest fire needs to be extinguished, and typically great expense is incurred for an airplane to supply an enormous amount of water to the scene of action. In this case the ability to trigger substantial rainfall would be highly desirable.
Another important application is an ecologically clean method for solar thermal energy collection with focusing plates, for example, in the form of parabolic troughs, wherein the total area of all the plates is as big as possible. On the one hand, it is preferable that the focusing plates are clean from dust. On the other hand, normally, the system occupies a big area in an open space, where natural dust always covers the plates, thereby reducing the efficiency of solar energy collection. The problem of cleaning the plates might be solved by repeated washings with distilled water.
Sometimes an effect of air saturated with water is unwanted, as for example, in plant growing incubators, where a desired high air temperature results in unwanted air saturation.
Given the ubiquitous nature of water in the vapor phase, it is possible to establish a sustainable water supply at virtually any location having air being refreshed, if one can develop a technology that efficiently harvests water from air.
Possession of such technology will provide a clear logistical advantage to supply agriculture, industry and townspeople with water and to control ecological conditions.
For example, a water production unit, which uses a desiccant wheel for extracting water from an air loop, where a portion of the air loop is heated using exhaust from, for example, a vehicle to regenerate the desiccant wheel, is described in U.S. Pat. No. 7,251,945 “Water-from-air system using desiccant wheel and exhaust” by Stephen Tongue. The method described assumes thermal energy consumption, and the suggested apparatus comprises moving parts of the mechanism.
Another method for extracting water from air is described by Spletzer, in three U.S. Pats. No. 6,360,549—Method and apparatus for extracting water from air; U.S. Pat. No. 6,453,684—Method and apparatus for extracting water from air; and U.S. Pat. No. 6,511,525—Method and apparatus for extracting water from air using a desiccant. The method is described as four steps: (1) adsorbing water from air into a desiccant, (2) isolating the water-laden desiccant from the air source, (3) desorbing water as vapor from the desiccant into a chamber, and (4) isolating the desiccant from the chamber, and compressing the vapor in the chamber to form a liquid condensate. The described method assumes electrical energy consumption, and the suggested apparatus comprises moving parts.
In both of the above approaches there is a need for energy consumption and mechanisms comprising moving parts, thereby requiring a degree of maintenance of the systems. This makes the water harvesting neither reliable nor inexpensive. Moreover, the fuel or electrical energy consumption renders these prior art methods unclean ecologically.
Yet another method and apparatus for atmospheric water collection is described in U.S. Pat. No. 7,343,754, “Device for collecting atmospheric water” by Ritchey. This method is based on moist air convection due to the temperature difference between air and ground. However, such slow convection does not allow for producing industrial amounts of water.
U.S. Pat. No. 6,960,243, “Production of drinking water from air” by Smith, et al, describes an adsorption-based method and apparatus, where the adsorption process is modified to reduce heating energy consumption. However, the adsorption method is also intended for producing small quantities of water.
The water condensation process is an exothermal process. I.e., when water is transformed from vapors to aerosols and/or dew, so-called latent-heat is released, thereby heating the aerosols and/or dew drops themselves, as well as the surroundings. The pre-heated aerosols and/or dew drops subsequently evaporate back to gaseous form, thereby slowing down the desired condensation process.
To moisturize and clean eye-glasses, one breathes out a portion of warm and humid air through widely opened mouth, while a blowing through a tiny hole between folded lips is substantially less efficient for the moisturizing.
FIG. 1 is a schematic drawing of a classical prior art profile of an airplane wing 10. It is well-known that there is a lift-effect of the airplane wing 10, which is a result of the non-symmetrical profile of wing 10. An oncoming air stream 12 flows around the non-symmetrical profile of wing 10, drawing forward the adjacent air due to air viscosity, according to the so-called Coanda-effect. The axis 11 of wing 10 is defined as separating the upper and lower fluxes. Axis 11 of wing 10 and the horizontal direction of the oncoming air flux 12 constitute a so-called “attack angle” 13. Firstly, a lifting-force is defined by attack angle 13, which redirects the flowing wind. Secondly, when attack angle 13 is equal to zero, wing 10, having an ideally streamlined contour, provides that the upper air flux 14 and the lower air flux 15 meet behind wing 10. Upper air flux 14 and lower air flux 15, flowing around wing 10, incur changes their cross-section areas and are accelerated convectively according to the continuity principle: pSv=Const, where p is the density of flux; v is the flux velocity, and S is the flux cross-section area. As a result, upper air flux 14, covering a longer way, runs faster, than lower flux 15. According to Bernoulli's principle, this results in less so-called static pressure on wing 10 from upper flux 14 than the static pressure from the lower flux 15. If upper flux 14 and lower flux 15 flow around wing 10 laminary, the difference of the static pressures is defined as
            Δ      ⁢                          ⁢      P        =          C      ⁢                          ⁢      ρ      ⁢                        v          2                2              ,where ΔP is the static pressure difference defining the lifting force when attack angle 13 is equal to zero, C is the coefficient, depending on wing 10's non-symmetrical profile, p is the density of the air; and v is the velocity of the air flux relatively to wing 10. In practice, there are also turbulences and vortices of the fluxes, which are not shown here. The general flowing, turbulences and vortices result in air static pressure distribution, particularly, in local static pressure reduction and local extensions of the flowing air. Considering a certain portion of air flowing around wing 10, and referring to the Klapeiron-Mendeleev law concerning a so-called hypothetic ideal gas state:
                    P        ⁢                                  ⁢        V            T        =          n      ⁢                          ⁢      R        ,where n is the molar quantity of the considered portion of the gas, P is the gas static pressure, V is the volume of the gas portion, T is the absolute temperature of the gas, and R is the gas constant, there are at least two reasons for changes in the gas state parameters of the air portion flowing around wing 10. First, for relatively slow wind, when the flowing air can be considered as incompressible gas, Gay-Lussac's law for isochoric process bonds the static pressure P with absolute temperature T by the equation
                    Δ        ⁢                                  ⁢        P            P        =                  Δ        ⁢                                  ⁢        T            T        ,i.e. reduced static pressure is accompanied with proportional absolute temperature decreasing ΔT. Second, for wind at higher speeds, running on a non-zero attack angle 13, when the air becomes compressible-extendable, the wind flowing around wing 10 performs work W for the air portion volume extension, wherein the volume extension process is substantially adiabatic. The adiabatic extension results in a change of the portion of gas internal energy, accompanied with static pressure reduction and temperature decrease. The work performed W of the wind flowing around wing 10 for the adiabatic process is defined as: W=nCVΔTa, where CV is the heat capacity for an isochoric process, and ΔTa is the adiabatic temperature decrease of the considered air portion. The value of the adiabatic temperature decrease ΔTa=T2−T1 is bonded with static pressure reduction by the relation: T2/T1=(P2/P1)(γ−1)/γ, where P1 and P2 are static pressures of the considered air portion before and after the considered adiabatic process correspondingly, and γ is an adiabatic parameter, which depends on molecular structure of gas, and the value γ=7/5 is a good approximation for nature air. Local cooling by both mentioned processes: isochoric and adiabatic pressure reduction, acts in particular, as a water condensation trigger. Moreover, if the wind flows around a wing with a velocity equal to or higher than the Mach number, i.e. the speed of sound, a well-known phenomenon of shock sound emission takes place. This shock wave is not caused by wing vibration, but it is at the expense of the internal energy of the air flow, that results in an air temperature shock decrease and thereby, provokes the process of vapor condensation into water-aerosols. For example, as is shown schematically in FIG. 1a, considerable amounts of water-vapor condense into water-aerosols 17 and sublimate into micro-flakes-of-snow 18, which are observed behind the high-speed aircraft's 16 wings.
Reference is now made to prior art FIG. 1b, a schematic illustration of a convergent-divergent nozzle 100, also known as the De Laval nozzle, and graphics of distribution of two parameters of gas 101: velocity 150 and static pressure 160 along the length of nozzle 100. A standard rocket nozzle can be modeled as a cylinder 140 that leads to a constriction 141, known as the “throat”, which leads into a widening “exhaust bell” 142 open at the end. High speed, and therefore compressible-extendable hot gas 101 flows through throat 141, where the velocity picks up 151 and the pressure falls 161. Hot gas 101 exits throat 141 and enters the widening exhaust bell 142. It expands rapidly, and this expansion drives the velocity up 152, while the pressure continues to fall 162. The gas absolute temperature distribution along the length of nozzle 100 (not shown here) is similar to the static pressure distribution 160.
FIG. 2 is a prior art table showing figures for weather conditions near the ground and how much water is in the air. Each cell 22 of the table comprises two numbers: upper and lower. The upper numbers show the “absolute humidity” in g/m3, i.e. how many grams of water-vapors are in one cubic meter (1 m3) of air. The lower numbers show so-called “dew-point” temperature of the air in ° C. For example, at the air temperature of 35° C. and relative humidity of 70%, the absolute humidity is 27.7 g/m3 and the dew-point temperature is 28° C.
FIG. 2a is a prior art schematic representation of a breeze flux 24, crossing through a cube 21 of space, having all the dimensions of 1 m. If, for example, the breeze velocity is given as v=5 m/sec, thereby, considering the described humidity conditions, each second (27.7×5=138.5) gram of water-vapors cross through space cube 21. This means that approximately ½ ton of water-vapors crosses space cube 21 per hour.
FIG. 3a is a prior art schematic illustration of a well-known “vortex tube”, also known as the Ranque-Hilsch vortex tube. It is a mechanical device 300 that separates a compressed gas 310 into hot 311 and cold 312 streams. It has no moving parts. Pressurized gas 310 is injected tangentially into a swirl chamber 313 and accelerates to a high rate of rotation. Due to a conical nozzle 314 at the end of the tube 315, only the outer shell of the rotated gas 316 is allowed to escape at the butt-end outlet 317. As a result this portion 311 of the gas is found to have been heated. The remainder of gas 316, which performs an inner vortex of reduced diameter within the outer vortex, is forced to exit through another outlet 318. As a result this portion 312 of the gas is found to have been cooled.
FIG. 3b is a simplified exemplary prior art schematic illustration of the phenomenon of atmospheric tornados arising. If viscous air streams 32 and 33, having equal velocities at their propagation fronts, meet at an angle of almost 180°, friction between contacting parts of viscous air streams 32 and 33 results in re-distribution of air streams 32 and 33 fronts' velocities, as shown schematically by arrows 34 and 35. The re-distributed velocities redirect the fronts such that portions of air move angularly, as it is shown schematically by circulating arrows 36, and the two air streams 32 and 33 suck portions of each other according to the Coanda-effect. In addition, fresh portions of air streams 32 and 33 make new portions of the circulating vortex in the same space. Such a positive feedback loop may create local tornados having a high spin rate, wherein outer rotating air portions, which are speeding faster, suck new portions of air according to Bernoulli's principle and the Coanda-effect, and there is an inherent relative vacuum near the air rotation center. The portions of the rotating air at the same time can move vertically, so air portions move helically-vertical. A tornado is not necessarily visible; however, the intense low pressure, caused by the high wind speeds and rapid rotation, usually causes water-vapor in the air to condense into a visible condensation funnel. Thus, a phenomenon is observed that quickly circulating air triggers condensation of vapor molecules into water-aerosols. It may happen even if there are no dew-point conditions for water condensation in the nearest surroundings of the tornado. There are at least two mechanisms for triggering water condensation. One mechanism is explained by the fact that circulating air has inherent pressure distribution, wherein inner pressure is lower and outer pressure is higher. An air portion, which is entrapped by the high spin tornado, is convectively accelerated and adiabatically decompressed by the cyclone. Static pressure is reduced due to both the convective acceleration and adiabatically. The static pressure reduction is accompanied with a decrease in air portion temperature. The air cooling provokes the water vapors to condense into aerosols. Another trigger for water condensation derives from the fact that quickly revolving air, accompanied inherently by friction between the moving moist air parts, causes the phenomenon of water-vapor molecules ionization. The ionized molecules become the centers for condensing water polar molecules into easily visible aerosols.
There is therefore a need in the art for a system to provide an effective and ecologically clean mechanism for controlled water harvesting from air. Wind energy has historically been used directly to propel sailing ships or conversion into mechanical energy for pumping water or grinding grain. The principal application of wind power today is the generation of electricity. There is therefore a need in the art for a system to provide an effective mechanism for water harvesting from air utilizing nature wind power.